A man was sentenced to 14 years in prison after he was caught impersonating Justin Bieber on the web in order to convince teen girls to perform sex acts on camera.

Robert Hunter, 35, of Middlesborough, England was arrested on multiple counts of inciting a child to engage in sexual activity and making indecent photos after one of his victims came forward.

Police who searched Hunter's computer found some 800 videos of both girls and boys — some as young as nine — performing various sexual acts.

According to the prosecution, by pretending to be Bieber, Hunter was able to persuade hundreds of girls from around the world to record themselves stripping in exchange for "being their boyfriend."

Hunter would then use the videos from the girls to convince young boys to perform similar acts on camera, and use those videos "to lure more girls."

When a victim tried to back out of the arrangement, Hunter would threaten to release their explicit footage on social networks.

On one occasion, Hunter made good on his threat by posting indecent photos of a 12-year-old girl on Facebook along with identifying information.

That girl reportedly cut herself in response.

"It represents callous, almost sadistic exploitation over a number of years preying on girls' naivety who were undermined by their own behaviour," said Judge Peter Bowers, who called the Hunter's scheme "one of the most serious cases of internet abuse that the courts have dealt with."

Judge Bowers hoped the parents of teenage children will see the case as a warning "of what can be done via the Internet."